Safer by Design: ‘Meta’ Review Examines Expanding Branches of Green Chemistry

Wednesday, June 13, 2018

Back in 1998, Paul Anastas co-authored a book that introduced 12 principles of “green chemistry,” an emerging field he’d been promoting at the U.S. Environmental Protection Agency to make chemistry and the related processes cleaner and safer through scientific design. Among other challenges, it called for greater efforts to prevent waste, the reduction or elimination of the use of hazardous chemicals, and a focus on safer solvents

Two decades later the principles of green chemistry infiltrate nearly every industrial sector — from the production of food and energy to the pharmaceutical and cosmetics sectors — and are taught at universities across the world.

green chemistry 20 years cover
In a new review paper, published in the journal Green Chemistry in celebration of the 20th anniversary of the book, Anastas, now a professor at Yale, and a team of co-authors document the range of scientific research and inventions that have emerged from green chemistry. Framed around those 12 principles, the “meta-review” explores the growth achieved within each of the principles — highlighting specific examples and tools that have transformed the world of chemistry — and identifying areas where challenges and opportunities remain.
“There have been literally hundreds, if not thousands, of review papers over the years looking at breakthroughs in bio-based materials, or catalysis, or new solvents, and other green chemistry advances,” said Anastas, the Teresa and H. John Heinz III Professor in the Practice of Chemistry for the Environment at Yale and director of the Center for Green Chemistry and Green Engineering at Yale (CGC&GE).
“But no one has ever conducted a meta-review across the entire field — something that illustrates all of the areas that have emerged, areas where there has been great progress, and quite frankly areas where there has not been much activity. That’s what this paper attempts to do.”
Inspired by the iconic tree diagrams that illustrate the range of applications for particular raw materials, the paper also introduces an illustrated “Green ChemisTREE,” which charts the diversity of research and achievements stemming from each of the principles.
“The biggest challenge was certainly assembling and condensing the vast amounts of green chemistry knowledge that is out there,” said Hanno Erythropel, a postdoctoral associate at Yale and lead author of the review. The team of 16 authors represent the Center for Green Chemistry and Green Engineering at Yale, a multidisciplinary center that integrates students and researchers from the Yale School of Forestry & Environmental Studies, the Yale School of Arts and Sciences, and the Yale School of Engineering and Applied Sciences.
In the mid-1990s, green chemistry was rarely highlighted outside of niche symposia and the occasional publication. Now, a growing network of scientists can access multiple dedicated journals, handbooks and encyclopedias, conferences, training courses, software tools, databases, funding sources and award programs.
There have emerged multiple sub-fields that are growing on the peripheries of toxicology, engineering and other scientific disciplines. Metrics of academic research show that there are more than 300 green chemistry-themed articles that have been cited at least 100 times.
And these advances have penetrated nearly every industrial sector:
  • The pharmaceutical industry, for instance, has made significant progress in waste prevention through simpler processes in the manufacture of products, such as ibuprofen.
  • Scientists have developed analytic processes to evaluate the safety of chemical synthesis, including tools that score the safety of each chemical within a process.
  • Chemical companies have developed processes to produce industrial chemicals while generating only water as co-products.
  • And researchers have developed systems to replace volatile and often toxic solvents with water.

“Green chemistry has touched every business sector that I can imagine, from food to energy, to plastics, to drugs, to cleaning, to cosmetics,” said Anastas. “There’s so much going on.”
To illustrate the diversity and range of green chemistry, the research team devised the Green ChemisTREE diagram, led by Julie Zimmerman, Professor of Green Engineering and Assistant Director for Research at the CGC&GE, in close collaboration with Hanno Erythropel. 
“In the diagram, the branches represent each of the principles of green chemistry while the leaves represent the techniques available to the green chemist — including mechanisms, procedures, design guidelines, and other resources they can use to advance the discipline,” Zimmerman said.
The authors expect that the tree will continue to grow. “Green Chemistry has always been envisioned as a philosophy of continuous improvement,” they write. “(Green) Chemists will constantly question what can be done better, what experiments and collaborations would be a step in the right direction, and how we know we have made progress.”

Contributed by Kevin Dennehy, Associate Director of Communications, School of Forestry and Environmental Studies